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SY4307A

Field	Value
image	SY4307AFace.jpg
image_size	150px
caption	Standard Telephones and Cables/Brimar brand Australian Pentode, type SY4307A, c1940
classification	Power Output Pentode
service	Class C amplifier, (Radio Frequency)
height_in
diameter_in
weight_lbs
cathode_type	Directly heated
filament_voltage	5v
filament_current	1A
max_dissipation	6W
max_voltage	500v
pinout	American 5 Pin, (UX5)

reference	4307A datasheet

with side locating pin between pis 1 and 2.

Pin 1, Heater/Cathode

Pin 2, Screen Grid, g2

Pin-3, Control Grid, g1

Pin-4, Suppressor Grid

Pin-5, Heater/Cathode

Top Cap, Anode/Plate

The type SY4307A is the STC version of the Western Electric 307A, a power output pentode possessing a similar power rating, but significantly different characteristics to the far more common type 807 thermionic valve/vacuum tube. The "SY" prefix denotes the site of manufacture as being Sydney. The plant, operated by Standard Telephones and Cables Pty. Ltd. was located on Mandible Street in the suburb of Alexandria and existed under that corporate entity from 1937 to 1970.. Although the remaining structure postdates the depicted device, this device was likely assembled on an adjoining property upon which the structures have been demolished and site re-purposed.

Electrically equivalent devices marked "307A" were manufactured in North America by Western Electric and these possibly predate the Australian version.

Uses

Although the 807 is used for both audio amplification, (usually class AB), and radio frequency amplification in the 1-30 MHz range, (usually class C), this type was usually used for the latter.

This tube/valve is a pentode with a 'directly heated cathode', meaning that the cathode consists of an emissive oxide coated filament. These features suggest the 4307A could predate and is contemporary with, the 807 which is a beam power tetrode, a more advanced design with a more linear transfer characteristic and a more complex 'indirectly heated cathode'.

Similarity to 807

If the pinout of the 4307A is compared to that of the 807 the similarity is striking. All pins are assigned equivalent electrodes with the exception of pin 4, which is the suppressor grid, g3, in this type but in the 807 pin 4 is connected to the equivalent of a suppressor grid, the 'beam plates' and also the separate indirectly heated cathode. It is possible to interchange the two with the relatively minor alteration involving the linking of pins 4 and 5 and ensuring the heater supply is floating (not connected to other heaters). If the heater is supplied from an A.C. source, linking pin 4 to the centre of that source and the cathode bootstrap minimizes hum pickup.

Historical significance

The STC/Brimar-made SY4307A was used extensively during World War II by the Australian armed forces and the example depicted is marked on the Bakelite collar of its base with the "D broad arrow D" commonwealth department of defense mark.

Two SY4307As were used, wired in parallel, as the output stage, or "final", in a transmitter constructed clandestinely by the Australian soldiers of Sparrow Force in Japanese occupied Portuguese Timor in 1942. This transmitter became known affectionately as "Winnie the War Winner ", named after the British wartime Prime Minister, Winston Churchill.

Image:SY4307ASide.jpg|Side view of SY4307A Image:SY4307AHtr01.jpg|View of directly heated cathode of the SY4307A Image:SY4307ABase.jpg|View of UX5 Base of the SY4307A

References

[https://frank.pocnet.net/sheets/136/3/307A.pdf WE307A datasheet]
[http://www.environment.nsw.gov.au/heritageapp/ViewHeritageItemDetails.aspx?ID=5062416 N.S.W. Office of Environment and Heritage]
[http://www.eoas.info/biogs/A001445b.htm Encyclopedia of Australian Science]

Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

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